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The charges against Tsang are in connection with his failure to file conflict of interest declarations to the Executive Council - the de facto cabinet - according to government-owned broadcaster RTHK.

They come less than a year after Hong Kong property tycoon Thomas Kwok and the government's former deputy leader Rafael Hui were jailed for graft after Hui was found guilty of taking bribes from Kwok and Kwok's brother Raymond.

While serving as chief secretary for administration, Hui was Tsang's deputy from 2005 to 2007.

He was jailed in December for seven and a half years on a total of five graft charges, making him the highest-ranking official in the city's history to be found guilty of taking bribes.

Prosecutors said Hui had enjoyed an extravagant standard of living that far outstripped his official salary, having spent millions on a mistress in Shanghai, for whom he bought gifts from bags, watches to properties.

He was accused of receiving HK$34 million (S$6.3 million) to be the Kwoks' "eyes and ears" in government.

Thomas was sentenced to five years over the payments while his brother Raymond was cleared.

As part of mitigation, Tsang wrote a letter to the court pleading for leniency for Hui.

Hong Kong has been seen as relatively graft-free but new cases have fuelled public suspicions over cosy links between authorities and industry leaders.

Concerns have also been raised about the role of the Chinese system of personal connections, or "guanxi", which greases the wheels of business.